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mumrah and hachikuji KAFKA-2334; Guard against non-monotonic offsets in the client (#5991)
After a recent leader election, the leaders high-water mark might lag behind the offset at the beginning of the new epoch (as well as the previous leader's HW). This can lead to offsets going backwards from a client perspective, which is confusing and leads to strange behavior in some clients.

This change causes Partition#fetchOffsetForTimestamp to throw an exception to indicate the offsets are not yet available from the leader. For new clients, a new OFFSET_NOT_AVAILABLE error is added. For existing clients, a LEADER_NOT_AVAILABLE is thrown.

This is an implementation of [KIP-207](https://cwiki.apache.org/confluence/display/KAFKA/KIP-207%3A+Offsets+returned+by+ListOffsetsResponse+should+be+monotonically+increasing+even+during+a+partition+leader+change).

Reviewers: Colin Patrick McCabe <colin@cmccabe.xyz>, Dhruvil Shah <dhruvil@confluent.io>, Jason Gustafson <jason@confluent.io>
Latest commit 1522929 Dec 14, 2018
Type Name Latest commit message Commit time
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bin KAFKA-7524: Recommend Scala 2.12 and use it for development (#5530) Oct 28, 2018
checkstyle Trogdor: Add Task State filter to /coordinator/tasks endpoint (#5907) Nov 27, 2018
clients KAFKA-2334; Guard against non-monotonic offsets in the client (#5991) Dec 14, 2018
config KAFKA-4514; Add Codec for ZStandard Compression (#2267) Oct 10, 2018
connect MINOR: Safe string conversion to avoid NPEs Dec 5, 2018
core KAFKA-2334; Guard against non-monotonic offsets in the client (#5991) Dec 14, 2018
docs MINOR: Replace tbd with the actual link for out-of-ordering data (#6035) Dec 14, 2018
examples KAFKA-7412: clarify the doc for producer callback (#5798) Nov 9, 2018
gradle KAFKA-7673: Upgrade rocksdb to 5.15.10 (#5985) Dec 6, 2018
jmh-benchmarks KAFKA-7612: Fix javac warnings and enable warnings as errors (#5900) Nov 13, 2018
log4j-appender/src KAFKA-7134: KafkaLog4jAppender exception handling with ignoreExceptio… Aug 29, 2018
streams MINOR: Update documentation for internal changelog when using table(). ( Dec 14, 2018
tests MINOR:Start processor inside verify message (#6029) Dec 14, 2018
tools/src MINOR: Add unit for max latency in ProducerPerformance output (#6014) Dec 12, 2018
vagrant MINOR: Switch to use AWS spot instances Oct 5, 2018
.gitignore KAFKA-6782: solved the bug of restoration of aborted messages for Glo… Jun 12, 2018
.travis.yml MINOR: Add HttpMetricsReporter for system tests Nov 9, 2017
CONTRIBUTING.md KAFKA-2321; Introduce CONTRIBUTING.md Jul 27, 2015
HEADER trivial fix to add missing license header using .gradlew licenseForma… Feb 7, 2014
LICENSE KAFKA-4514; Add Codec for ZStandard Compression (#2267) Oct 10, 2018
NOTICE MINOR: Update copyright year in NOTICE Feb 5, 2018
PULL_REQUEST_TEMPLATE.md MINOR: Exclude Committer Checklist section from commit message Nov 10, 2017
README.md MINOR: Bump Gradle version to 5.0 (#5964) Nov 30, 2018
TROGDOR.md KAFKA-7514: Add threads to ConsumeBenchWorker (#5864) Nov 13, 2018
Vagrantfile MINOR: Switch to use AWS spot instances Oct 5, 2018
build.gradle MINOR: Bump Gradle version to 5.0 (#5964) Nov 30, 2018
doap_Kafka.rdf MINOR: Remove <release> tag from doap file May 12, 2016
gradle.properties KAFKA-7524: Recommend Scala 2.12 and use it for development (#5530) Oct 28, 2018
jenkins.sh KAFKA-5887; Replace findBugs with spotBugs and upgrade to Gradle 4.10 Sep 10, 2018
kafka-merge-pr.py MINOR: Bump version to 2.2.0-SNAPSHOT Oct 5, 2018
release.py MINOR: Improve maven artifactory url in release.py (#5931) Nov 20, 2018
release_notes.py MINOR: Change version format in release notes python code Nov 3, 2017
settings.gradle MINOR: Enable ignored upgrade system tests - trunk (#5605) Sep 13, 2018
wrapper.gradle KAFKA-1490 remove gradlew initial setup output from source distributi… Sep 23, 2014


Apache Kafka

See our web site for details on the project.

You need to have Gradle and Java installed.

Kafka requires Gradle 4.7 or higher.

Java 8 should be used for building in order to support both Java 8 and Java 11 at runtime.

Scala 2.12 is used by default, see below for how to use a different Scala version or all of the supported Scala versions.

First bootstrap and download the wrapper

cd kafka_source_dir

Now everything else will work.

Build a jar and run it

./gradlew jar

Follow instructions in http://kafka.apache.org/documentation.html#quickstart

Build source jar

./gradlew srcJar

Build aggregated javadoc

./gradlew aggregatedJavadoc

Build javadoc and scaladoc

./gradlew javadoc
./gradlew javadocJar # builds a javadoc jar for each module
./gradlew scaladoc
./gradlew scaladocJar # builds a scaladoc jar for each module
./gradlew docsJar # builds both (if applicable) javadoc and scaladoc jars for each module

Run unit/integration tests

./gradlew test # runs both unit and integration tests
./gradlew unitTest
./gradlew integrationTest

Force re-running tests without code change

./gradlew cleanTest test
./gradlew cleanTest unitTest
./gradlew cleanTest integrationTest

Running a particular unit/integration test

./gradlew clients:test --tests RequestResponseTest

Running a particular test method within a unit/integration test

./gradlew core:test --tests kafka.api.ProducerFailureHandlingTest.testCannotSendToInternalTopic
./gradlew clients:test --tests org.apache.kafka.clients.MetadataTest.testMetadataUpdateWaitTime

Running a particular unit/integration test with log4j output

Change the log4j setting in either clients/src/test/resources/log4j.properties or core/src/test/resources/log4j.properties

./gradlew clients:test --tests RequestResponseTest

Generating test coverage reports

Generate coverage reports for the whole project:

./gradlew reportCoverage

Generate coverage for a single module, i.e.:

./gradlew clients:reportCoverage

Building a binary release gzipped tar ball

./gradlew clean releaseTarGz

The above command will fail if you haven't set up the signing key. To bypass signing the artifact, you can run:

./gradlew clean releaseTarGz -x signArchives

The release file can be found inside ./core/build/distributions/.

Cleaning the build

./gradlew clean

Running a task with a particular version of Scala (either 2.11.x or 2.12.x)

Note that if building the jars with a version other than 2.12.x, you need to set the SCALA_VERSION variable or change it in bin/kafka-run-class.sh to run the quick start.

You can pass either the major version (eg 2.12) or the full version (eg 2.12.7):

./gradlew -PscalaVersion=2.12 jar
./gradlew -PscalaVersion=2.12 test
./gradlew -PscalaVersion=2.12 releaseTarGz

Running a task with all scala versions

Append All to the task name:

./gradlew testAll
./gradlew jarAll
./gradlew releaseTarGzAll

Running a task for a specific project

This is for core, examples and clients

./gradlew core:jar
./gradlew core:test

Listing all gradle tasks

./gradlew tasks

Building IDE project

Note that this is not strictly necessary (IntelliJ IDEA has good built-in support for Gradle projects, for example).

./gradlew eclipse
./gradlew idea

The eclipse task has been configured to use ${project_dir}/build_eclipse as Eclipse's build directory. Eclipse's default build directory (${project_dir}/bin) clashes with Kafka's scripts directory and we don't use Gradle's build directory to avoid known issues with this configuration.

Publishing the jar for all version of Scala and for all projects to maven

./gradlew uploadArchivesAll

Please note for this to work you should create/update ${GRADLE_USER_HOME}/gradle.properties (typically, ~/.gradle/gradle.properties) and assign the following variables


Publishing the streams quickstart archetype artifact to maven

For the Streams archetype project, one cannot use gradle to upload to maven; instead the mvn deploy command needs to be called at the quickstart folder:

cd streams/quickstart
mvn deploy

Please note for this to work you should create/update user maven settings (typically, ${USER_HOME}/.m2/settings.xml) to assign the following variables

<settings xmlns="http://maven.apache.org/SETTINGS/1.0.0"

Installing the jars to the local Maven repository

./gradlew installAll

Building the test jar

./gradlew testJar

Determining how transitive dependencies are added

./gradlew core:dependencies --configuration runtime

Determining if any dependencies could be updated

./gradlew dependencyUpdates

Running code quality checks

There are two code quality analysis tools that we regularly run, spotbugs and checkstyle.


Checkstyle enforces a consistent coding style in Kafka. You can run checkstyle using:

./gradlew checkstyleMain checkstyleTest

The checkstyle warnings will be found in reports/checkstyle/reports/main.html and reports/checkstyle/reports/test.html files in the subproject build directories. They are also are printed to the console. The build will fail if Checkstyle fails.


Spotbugs uses static analysis to look for bugs in the code. You can run spotbugs using:

./gradlew spotbugsMain spotbugsTest -x test

The spotbugs warnings will be found in reports/spotbugs/main.html and reports/spotbugs/test.html files in the subproject build directories. Use -PxmlSpotBugsReport=true to generate an XML report instead of an HTML one.

Common build options

The following options should be set with a -P switch, for example ./gradlew -PmaxParallelForks=1 test.

  • commitId: sets the build commit ID as .git/HEAD might not be correct if there are local commits added for build purposes.
  • mavenUrl: sets the URL of the maven deployment repository (file://path/to/repo can be used to point to a local repository).
  • maxParallelForks: limits the maximum number of processes for each task.
  • showStandardStreams: shows standard out and standard error of the test JVM(s) on the console.
  • skipSigning: skips signing of artifacts.
  • testLoggingEvents: unit test events to be logged, separated by comma. For example ./gradlew -PtestLoggingEvents=started,passed,skipped,failed test.
  • xmlSpotBugsReport: enable XML reports for spotBugs. This also disables HTML reports as only one can be enabled at a time.

Running in Vagrant

See vagrant/README.md.


Apache Kafka is interested in building the community; we would welcome any thoughts or patches. You can reach us on the Apache mailing lists.

To contribute follow the instructions here: